Last Christmas, he took a 1984 diesel truck and replaced its motor with a 1968 hot-rod engine with more horsepower. He then devised a wood-burning system with cooling and filtering units attached at the hood and in the pickup bed.

Keith estimates he has driven 4,000 miles since he converted the truck. The engine, which runs on hydrogen generated by burning the wood, is clean enough that Keith proudly shows off its clean spark plugs to the curious.

He keeps a 30-gallon trash can in the bed, filled with wood pieces that have already been burned to remove water. Keith fills a 6-foot reactor in the truck bed with wood, then starts up the engine. It still takes some gas to get the truck going, but within two minutes, the only fuel is wood. He also uses gas for a little extra power when he pulls his trailer.

The pickup has three pedals – brake, gas and wood. The farthest he has driven the truck is 100 miles in a day.

it’s far from emission-free — the wood has to burn, and that produces a lot of smoke and CO2. But Keith says,

“It takes about 20 pounds of wood to do what one gallon of gas will do,” he said. “But when I burn off the wood, you get the same emission you’d get if the wood just deteriorated on its own. You can’t say that about fossil fuels.”

Now, this is sort-of true, but I don’t think it’s true from the point of view relevant to air pollution. It’s true that if wood decays completely, it releases CO2 and water (vapor), and there are other things that seep into the ground. And if wood burns completely, it releases the same amount of CO2 and water vapor, and leaves ash which can be dumped on the ground. But I think it’s a rather big assumption that the word burns completely. Nothing burns completely except under very controlled conditions, and if you burn wood you will see huge amounts of smoke rising, and that smoke is certainly more than just CO2 and water vapor. (You can tell by the color — CO2 is clear and water vapor is white or clear.) It’s also ash and other particulate matter that pollutes the air — which is why you need a smokestack for a fireplace if you don’t want to choke from the fire. This is all pollution going into the air that otherwise would have stayed on the ground if the wood had merely decomposed naturally — and far more pollution than you’d get by burning an equivalent gallon of gasoline.

Which is part of the reason why, from the nineteenth century to the twentieth, we mostly switched over from burning wood for most things, to burning oil-based fuels. The trains that roared across the plains in the 1800s burned wood or coal, and produced a lot more pollution (per mile per unit of cargo/passengers) than the diesel trains or the gasoline cars of today.

In short, oil-based fuels like gasoline are far more environmentally-friendly than wood.

I’m very impressed by Mr. Keith’s engineering ability — and I’d absolutely love to see his truck in action — but sadly, I don’t think it would pass emissions inspection. But it certainly insulates him from increases in gasoline costs.

4 Responses to “Alternative Fuel”

The combustion of wood can be complete if the combustion process is so arranged as to have all decomposition/exhaust products exposed to temperatures in excess of 800degC in the presence of excess oxygen–but that’s not quite what he’s doing.

If he is raising the chopped wood to only a high enough temperature to remove almost all moisture, and this is stored for later use, and then the air incoming to the gassification reactor is preheated by outgoing gasses, and any water added is also preheated (water reacts with carbon above 800DegC or so to become burnable CO and H2), then the gasses produced will be burnable without particulate or volatile organic exhaust.